Oxidation of lower aliphatic alcohols



Patented 11, 1944 OXIDATION OF LOWER ALIPHATIC ALCOHOLS David 0. Hull, Kingsport, Tenn, asslgnor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application June 29, 1e42, Serial No. 448,957

3' Claims. (Cl. 260-531) This invention relates to the direct oxidation of organic compounds, particularly the oxidation of hydroxy compounds such as lower aliphatic alcohols oxidized directly to acids. x

This invention is a continuation-in-part of my allowed application, Serial No. 228,822, filed September 7, 1938, now Patent No. 2,287,803.

As pointed out in connection with the aforementioned companion application, in the prior art oxidation processes have required employing relatively high temperatures siich as 300 C. or 400 C. and the application of several steps. In other words, the oxidation either has not been direct, or if there has been direct conversion, the yields have been very low. 'For example, considering prior art procedure for converting ethanol to acetic acid, before my invention it was considered necessary to first dehydrogenate all of the ethanol and thereafter the aldehydic dehydrogenation product was converted to the acid which, as can be seen, involves a number of steps.

Carrying out oxidation processes in accordance with the prior art possesses a number of disadvantages exemplifled, for example, by the required use of relatively high temperatures. Also there may in some instances be the disadvantage of polymerization of the products of the starting materials accompanied by low yields and other losses.

In my companion application aforesaid I have described a process for a more direct oxidation of organic compounds. While the process of my application functions very satisfactorily and gives utilization of metals having anatomic number this invention is to provide a direct oxidation process which may be operated at relatively low temperatures and under ordinary pressure conditions, yet give very satisfactory yields of the desired oxidation products. -Still another object is to provide a direct oxidation process for the conversion of alcohols to acids wherein the alcohol may be converted, not only to an acid having a number of carbon atoms corresponding to the number of carbon atoms in the alcohol molecule, but also to a different acid. A still fur-. ther object is to provide a process which may be operated under other than normal atmospheric conditions, namely, under either superatmospheric or reduced pressures.

A further object is to provide a direct oxidation process that may be applied-to either alcohols alone or mixtures of alcohols and aldehydes, or other types of mixtures. A still further object is to provide a direct, low-temperature oxidation process which may beapplied to variou mixtures of alcohols and aldehydes wherein both the alcohol and the aldehyde are converted into adapted to the treatment of alcohols suchas butyl alcohol and the like wherein, not only may butyric acid be obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquids particularly adapted for employment in the aforesaid types of processes for good yields in relatively few steps, it involves the from 25 to 29. It is, therefore apparent that it,

is desirable, particularly under present conditions, to develop a process in order that other metals may be employed and the process improved in other respects, as will be apparent from the description which follows.

After further investigation I have found that I there are certain other catalytic materials which may be employed in direct oxidation processes in .a manner akin to the procedure set forth in my companion application which not only permits obtaining direct oxidation, but permits the production of a. relatively larger variety of products than has-heretofore been obtainable.

This invention has for one object to provide a process for the direct oxidation of organic compounds. Another object is to provide a direct oxidation process' which is particularly valuable for the direct conversion of lower aliphatic alcohols to lower aliphatic acids in substantially a single step. Still another object, however, is to provide a process which may also be applied to,

not only the monohydroxy alcohols, but to the polyhydroxy alcohols and other similar organic compounds. Another and particular object of the direct conversion of alcohols alone, or alcohols in various admixtures, into useful oxidation products. A still'further object is to provide methods for producing the catalysts as well as for activating and utilizing thecatalysts.

As already indicated, prior to myinvention if an alcohol were to be oxidized it was generally first dehydrogenated and then the dehydrogenation products further treated. In any event prior art processes as applied to alcohols usually involve the utilization of temperatures in excess of 300 C. which, .not only requires substantial heat input but, due to the higher temperatures and other conditions required in' handling chemicals, involves dangers of loss from polymerization or other undesired reactions; Also apparatus destruction may be more severe.

. I have found that contrary to such procedure an organic compound, exemplified in particular by a hydroxy compound as a lower aliphatic alcohol, may be directly oxidized at relatively low temperatures, even temperatures substantially below 0., with any of the usual oxidizing mediums of which the commonest one, namely air, may be readily utilized in my process. Also diy-procesa-after .it is placed in operation, does not usually require any heat input but generates sufficient heat itself to maintain the reaction.

Not only may single organic compounds be treated, but various mixtures of the organic compounds may be treated. For example, I have found that a-mixture comprising a lower aliphatic ,alcohol, together with a corresponding or a different aldehyde, maybe efli-ciently treated bymy novel process and catalyst to give veryhigh yields ofaliphatic acid. By my process and choice of catalyst it is possible to obtain one or more acids in the oxidation procedure. The. foregoing features, as well as features of treating various mixtures under different conditions, will be set forth in detail hereinafter.

While the oxidation procedure may be carried out in the apparatus described in the aforesaid companionapplication 228,822, now Patent No.

different constructions. For example, the preferred external construction would, in a large diameter unit, be in accordance with Hasche Patent 2,159,988. However, the construction may be a. sieve plate column, bubbl plate column, or other comparable arrangement for permitting the contact of an oxidizing medium containing free oxygen with the material to be oxidized. In the unit shown in the attached figure the column merely comprises an elongated; open column of relatively narrow dimensions. Attached to the lower part of the unit at 3 and 4, are cooling jackets provided with inlets for cooling medium as 'at 8 and I.

The upper part of the unit was provided with a similar jacket 8; however, in thisjacket, rather than cooling medium some heating medium may be circulated in the event that high boiling components are being directly oxidized or the reaction temperature is to be held lower than that which would'maintain a constant volume of catalyst. Inasmuch as the construction is substantially the same, however, the mechanical construction would be approximately the same and an inlet provided at 9, I and 6; outlets arepro- The lower part of the unit is provided with a plurality of inlet conduits, namely, inlet conduit I 4 which is connected with a temperature-controlled feed supply 16. Also leading into the lower part of the unit is an-inlet conduit I! for oxidizing medium.

The upper part of the unit is provided with a drawoif conduit I8 which leads through condenser it? into separator 2 i This separator has attached thereto a receiver 22 for condensate and a branch conduit 23 throughwhich non-condensables may be conducted to the scrubber 24.

The aforementioned scrubber is provided with a receiver 26 at the lower part thereof and, vent conduit 21 from the upper part thereof, which may lead through a meter or other device for measuring and testing the eiiiuents.

There may also be associated with the apparatus thermometers or other temperature controlling devices or various exchangers for recoverlng heat or otherwise facilitating or rendering the operation of the process more economical, or permitting it to be operated with automatic control. -Hence, my invention is not to be restricted in these respects.

I have found that certain metal compounds, as for example, esters derived from alkali and alkaline earth and the like metals, may be incorporated in acidic solutions and that these solutions will function as a catalyst medium for the direct oxidation of organic compounds." That is, an alcohol alone or alcohol and other organic compounds to be oxidized, may be passed into a catalyst solution, as aforementioned, in the presence of oxidizing medium containing free oxygen and thatthe alcohol may be directly oxidized to acid, as will be observable in greater detail from the specific examples which follow.

Referring to the various metals which I have tested, there may be mentioned sodium, barium, strontium, and lithium. Also potassium, rubidium, caesium, and calcium likewise operate in a comparable manner.

However, it will be observed that as respects the various metals that, for example, with the alkaline earth metals such as barium and strontium, a higher yield of a second acid may, under some circumstances, be obtained than in an instance when a derivative of an alkali metal such as sodium is employed as a catalyst.

In preparing catalyst solutions for use in the present process any convenient source of the metal may be employed such as salts, oxides or other derivative thereof. Preferably a derivative would be chosen which is easily soluble under conditions of the process. For example, assuming that it is desired to convert an alcohol such as ethanol or butanol directly to the corresponding aliphatic acid, the derivative of the catalyst metal would preferably be chosen corresponding to this acid. For example, in the instance of producing acetic acid there may be employed metal compounds such as sodium, strontium or other 'acetates,.depending upon the particular metal or metals employed. Furthertypical ex- 'amples of some of the metal derivatives which might be employed for producing the catalyst solution are: lithium acetate, rubidium acetate, caesium acetate, calcium acetate, magnesium acetate, and zinc acetate.

While the aforementioned metal derivatives may be employed in various organic liquids, which are solvents therefor, for simplicity of operation and minimizing the necessity of complicated separations I prefer to dissolve the catalyst compound in a liquid principally comprised of one of the materials which is to be produced in the process. For example, in the event my process was to be applied in converting butyl alcohol directly into butyricacid I would preferably dissolve the catalyst compounds in an aliphatic acid 'such as butyric acid. .However, propionicor acetic acid could also be used. However, for initially preparing the catalyst solution other liquids could be employed, as for example, organic esters and the like such as butyl or ethyl acetate.

In any event, irrespective of the exact metal compound and the liquid that the compound is dissolved in, the catalyst solution would be given a vigorous oxidation treatment such as blowing with a substantial amount of air usually for a period of at least 5 or 10 minutes, and if desired for several hours. preferably be accompanied by the introduction This treatment would assent? of an aldehyde along with the oxidizing medium and functions to convert the metal ions of the catalyst metal into a higher state of valence than their lowest valence. The treatment may be accompanied by heating obtained in any convenient manner such as byflowing a heating atmospheric pressure as this permits the inclusion of a larger amount of oxidizing mediumzand fully saturates the catalyst liquid.

After the catalyst liquid containing an alkaline earth or alkali metal compound as already described, has been treated and brought to a starting temperature, usually above room temperature but below around 100 C., the organic compound to be oxidized may be supplied to the Process.

That is, referring to the attached drawing, the oxidation column 2 is filled with the catalyst liquid comprising one or more alkali, or alkaline earth metal compounds of the type described dissolved in solvent and maintained at the desired temperature. The hydroxy compound to be oxidized is introduced into the oxidation process through conduit I4 and the oxidizing medium, usually air (however pure oxygen or'ozone may be em oyed and appear to render the catalyst solution more active, but are not necessary), and the compound oxidized to one or more desired oxidation products, as will be described hereinafter.

Assuming that the oxidation product is a liquid, a portion thereof may be volatilized or pumped oil through conduit l8 through the condenser l9 also be observed that apparently the alkaline earth metal catalyst gave high yields of the propionic acid. While a 4% catalyst solution has been indicated, the amount of catalyst 'may vary from' a small amount to a saturated solution, but in general the amount of catalyst will be maintained between 1% or 2% and 12%.

While the foregoing examples are illustrative of one of the preferred applications of my process, my process may be .operated with the various other catalysts referred to and under various other conditions, as will be apparent from the examples which follow:

Erample IV On this ratio. there was obtained about m 60 unox'idized organiccompound and the like components, uncondensed, pass through conduit 23 into scrubber 24 where they are recovered. While only a single scrubbing unit has been indicated,

a plurality of such units may be employed or grams of butyric acid and 10 to grams of propionic acid as the major products of the oxidation process. As in the preceding examples, the process was operated so that the catalyst solution was maintained in the liquid phase. However, in the instance of alcohol, as butyl alcohol, it is possible, if it is desired to operate with temperatures up to nearly 150 C. that a higher temperature can be applied if pressure is applied to the reaction. In this reaction some excess oxidizing medium (air)- was supplied to the reaction so that a content of oxygen was indicated in the oil'gases.

Example V In accordance with thisrexample the same materials, namely, ethanol and ,acetaldehyde,

' were treated as referred to in the immediately preceding example. However, the proportions of The conversion of a substantial amount of alco- I' I Per cent Per Weight w i M Weight Weight. converted Per cent Per cent meta butyl e g bu c propionic to propionic conversion conversion Metal acetate salt in aeetalde- (mm t alcohol hyde ed 11 acid,6d and biggie propiignic mm on led I produced produ 2J5 I ac "Grim" Gram: Gram 0mm:

I. Barium I 4 400 %.5 24.4 V11. 67 5.57 6.1

II. Strontium- 4 256 512. 21.8 17.2 18.55 6.83 6.72 HI. odinm 4 363 725 43.21 10.29 12.84 10.01 2.83

hol directly to acid continued to take place. Also in this example the preferred operating tern- I 'perature between 30 C. and 50 C. was reduced to approximately 0 C. However, direct conversion of the alcohol to acid continued to take.

place, but somewhat slower than at the higher temperatures.

. Example VII In accordance with this example the apparatus and catalyst, namely, alkaline earth metal salts, as. in the preceding description, were like-- wise employed. However, a secondary alcohol, namely, isopropyl alcohol, was fed to the process and a substantial yield of ketone was obtained.

' There was also obtained several per cent of acetic acid and a small amount of esters such as isopropyl acetate.

Example VIII a sizable yield of methyl ethyl ketone was obtained and a yield of acetic and propi onic acid.

'- trample IX In this example secondary amyl alcohol was directly oxidized, giving methyl propyl ketone between 10% and 60%, some secondary amyl ester and varying amounts of" propionic and acetic acid up to 20%.

In the foregoing examples there was some alcohol left unchanged which may be recovered either in the scrubber or otherwise. As indicated, while at normal atmospheric pressure a temperature under 100 C., 'and in many instances between 30 C. and 70 0., appears to be quite satisfactory, the process may be caused to operate even at temperatures as low as -5 C. and up to the boiling point of the catalyst solution.

In preferred operation using, for example,-the air as an oxidant, this may be supplied under some pressure and if desired a. rather substantial excess can be incorporated, although for normal operations only an excess, merely so that a few per cent of oxygen are indicated in the 'ediuents, would be employed. In the event of the use of other oxidants such as relatively pure oxygen and ozone, smaller amounts are required and may be supplied undr substantial pressure for causing them to fully permeate the entire cata- 127st solution.

While in certain of the foregoing examples we have indicated the utilization of butyl alcohol in admixture with aceteldehyde, a comparable mixture of ethyl alcohol and butyraldehyde may be processed in the some manner to obtain a mixture of acetic and butyrlc acids. Similar remarks apply to the employment of other mixtures of alcohols and aldehydes. That is, ethyl alcohol may be processed in admixture with acetaidehyde'to produce relatively pure acetic acid. Or, for example, propyl alcohol may be processed in accordance with the present invention in the presence of ecetaldehyde, butyraldehyde, or propionaldehyde. However. inasmuchas acetaldehyde is in many instances most readily available and has a low boiling point, it would preferably be employed along with the other alcohols such as butyl alcohol; amyl alcohol, and the like as representing the most economical procedure as well as tending to lower the boiling points and permittingthe functioning of the process at' lowest tempera tures.

As already indicated, the pressure may be varled over wide limits without basically changing the process. However, since the process functions satisfactorily under normal atmosconditions except that in some instances, such as for saturating the catalyst. solution with oxygen, I may apply a few pounds pressure up to 2 or 3 atmospheres for this purpose. Also, as indicated, the process functions Very well'at ordinary temperatures of 30 C. to 70 C. However, by raising the temperatures above the range indicated and applying some increased pressure,

larger amounts of alcohol may be converted per pass per unit of time. Under such procedure the aldehyde feed would be correspondingly reduced as the amount of alcohol fed was increased.

As apparent from certain of the preceding examples one valuable aspect of the present invention is that acids having fewer carbon atoms than the alcohol being oxidized may be directly produced and the proportion of these other acids to the acid having the same number of carbon atoms as the alcohol being oxidized may be varied by choice of the particular catalyst, as apparent from Examples I, II and DI set forth above.

It is apparent from the foregoing that my invention is applicable to the direct oxidation of the various organic compounds, particularly hydroxy compounds such as various alcohols. The foregoing examples ar merely illustrative of some of the materials to which my low temperature liquid phase process may be applied, but various other compounds, such as hydroxy alcohols exemplified. by glycols, may be treated in a comparable manner. Hence, I do not wish to be restricted in my invention excepting insofar as is necessitated by the prior art and the spirit of the appended claims.

What I claim and desire to secure by Letters Batent of the United States is:

1. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises treating a solution of a metal'ion-of a metal of the alkali and alkaline earth metal groups in an aliphatic acid with an aldehyde and a gaseous oxidizing me-.

' suiting solutionof catalyst, alcohol and aldehyde pheric pressures I. prefer to opera% under such by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase, and subsequently recovering the aliphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which. comprises treating a solution of a. metal ion of a metal of the alkali and alkaline earth metal groups in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form a catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol or the resulting solution of catalyst, alcohol and aldehyde by treating said solution with a gaseous oxidizing medium, maintaining the temperature of the solution of catalyst, alcohol and aldehyde during its treatment with the gaseous oxidizing medium such that the solution is maintained in the liquid phase at a temperature of from 5 to C. and subsequently recovering the aliphatic acid produced.

3. A process for the direct oxidation of a lower aliphatic alcohol to obtain the corresponding aliphatic acid, which comprises'treating a solution of a sodium salt in an aliphatic acid with an aldehyde and a gaseous oxidizing medium to form a catalyst solution, introducing material amounts of a lower aliphatic alcohol and a lower aliphatic aldehyde into the activated catalyst solution, oxidizing the alcohol of the resulting solution of catalyst, alcohol and aldehyde by treat- 

